One of the problems faced by the perfumery industry lies in the relatively rapid loss of the olfactive benefit provided by odoriferous compounds due to their volatility, particularly that of “top-notes”. This problem is generally tackled using a delivery system, e.g. capsules containing a perfume, to release the fragrance in a controlled manner.
In order to be successfully used in consumer products, perfume delivery systems must meet a certain number of criteria. The first requirement concerns stability in aggressive medium. In fact delivery systems may suffer from stability problems, in particular when incorporated into surfactant-based products such as detergents, wherein said systems tend to degrade and lose efficiency in the perfume-retention ability. It is also difficult to have a good stability and a good dispersion of the capsules altogether. The dispersion factor is very important because the aggregation of capsules increases the tendency of the capsule-containing product to phase separate, which represents an important disadvantage. On the other hand, perfume delivery systems must also perform during the actual use of the end-product by the consumer, in particular in terms of odor performance, as the perfume needs to be released when required. Another challenge faced by the perfumery industry is to provide delivery systems that are well deposited on the substrate for the treatment of which the end product is intended to be used, such as textile, skin, hair or other surfaces, so as to possibly remain on the substrate even after a rinsing step. To address this last specific problem, the use of cationic capsules has been described in the prior art. Cationic capsules are also known to be better dispersed in several applications.
For example, WO 01/41915 discloses a process for the preparation of capsules carrying cationic charges. Such a process is allegedly applicable to a large variety of microcapsules, in particular polyurethane-polyurea microcapsules are mentioned. After their formation, the capsules are placed in a medium which is favourable for the treatment with cationic polymers. The treatment with cationic polymers is carried out after purification of the basic capsule slurry, in order to eliminate anionic or neutral polymers which were not incorporated in the capsule wall during formation thereof, and other free electrically charged compounds involved in the encapsulation process. In particular, the capsules are diluted, isolated and then re-suspended in water, or even washed to further eliminate anionic compounds. After the purification step, the capsules are agitated vigorously and the cationic polymers are added. Partially quaternized copolymers of polyvinylpyrrolidones are cited to this purpose, among many other suitable polymers. The described process comprises several steps following the capsule formation, said process being therefore time consuming and not economically profitable.
US 2006/0216509 also discloses a process to render polyurea capsules positively-charged. This process involves the addition, during the wall formation, of polyamines, the capsules thus bearing latent charges, depending on the pH of the medium. Once formed, the capsules are subsequently cationized by acid action or alkylation to bear permanent positive charges. The cationic compounds therefore react with the capsule wall, chemically changing the latter.
WO2009/153695 from the applicant discloses a simplified process for the preparation of polyurea microcapsules bearing permanent positive charges based on the use of a specific stabilizer and which present good deposition on a substrate.
Deposition aids have also been described in prior arts in association with other types of capsules than polyurea-based ones. For instance WO2013/068255 relating to formaldehyde-free aminoplast-based microcapsules discloses in the process for the preparation of the microcapsules the option to add to the microcapsule dispersion a cationic polymer to improve deposition.
Despite those prior disclosures, there is still a need to improve the ability of delivery systems to deposit on a substrate and to adhere on the substrate in particular in the perfumery industry for leave-on applications and rinse-off applications, while being always performing in terms of perfume release and stability.
The microcapsules of the invention solve this problem as they proved to show improvement in terms of deposition properties compared to deposition aids disclosed heretofore.
The present invention provides new microcapsules for delivering an encapsulated material such as a perfume and/or other hydrophobic materials, which are coated with a particular composition of cationic copolymers.